Objectives To explore effectiveness and safety of polyglycosides of Tripterygium wilfordii (GTW) and mesalazine (5-aminosalicylic acid [5-ASA]) in preventing postoperative clinical and endoscopic recurrence of Crohn’s disease. Methods In this prospective, single-centre, single-blind study, postoperative Crohn’s disease patients in remission were randomized to receive 1 mg/kg GTW daily, orally, or 4 g 5-ASA daily, orally, for 52 weeks. Patients underwent physical examinations, ileocolonoscopies and biochemical analyses at baseline and weeks 13, 26 and 52, or when clinical recurrence was suspected. Outcome measures were proportion of patients showing clinical or endoscopic recurrence at week 52, and changes in Rutgeerts’ and Crohn’s Disease Activity Index (CDAI) scores. Results Twenty-one patients were assigned to receive GTW and 18 to 5-ASA; two patients on GTW and one on 5-ASA were withdrawn. Clinical and endoscopic recurrences were less common in the GTW group ( n = 4) versus the 5-ASA group ( n = 9). There were improvements in Rutgeerts’ scores for those taking GTW. Mean between-group CDAI scores were similar. No serious adverse events were reported. Conclusion These findings indicate that GTW appears to be an effective, well-tolerated prophylactic regimen, superior to oral 5-ASA, for preventing clinical and endoscopic recurrence in postsurgical Crohn’s disease.